The present invention is intended for use in an environment of a self-propelled vehicle or other piece of equipment which is powered by a known form of internal combustion engine. The invention is preferably designed for use in connection with a vehicle or other equipment powered by a diesel engine.
Diesel engines do not use spark plugs. Rather, they rely for ignition of the fuel-air mixture on compression of that mixture by rapid motion of a piston to reduce the volume of a fuel-air charge in the combustion chamber.
When a diesel engine is started, however, known glow plugs are used to assist in providing engine starting ignition. The glow plugs typically are operated for a brief time.
Vehicles of the type forming the environment for the present invention are commonly heavy-duty military and commercial vehicles such as trucks, buses, infantry fighting vehicles, tanks, and others. Because such vehicles are typically operated by a large number of operators having different skill levels, considerable warning and protection equipment is incorporated into such vehicles. This warning and protection equipment includes means for informing an operator of the operations and conditions of certain vehicle and engine components.
The glow plugs of diesel engines are commonly controlled by a glow plug controller circuit. The glow plug controller circuit, upon an operator turning on the ignition, applies a high DC current, often in the neighborhood of 150 amps, to the glow plugs continuously during what is known as a "pre-glow" mode. A sensor detects the temperature of the engine and controls the pre-glow mode which endures for a period of time, typically 3-8 seconds. Following the pre-glow portion of the cycle, the glow plug controller shifts to an "afterglow" portion of the cycle. During the afterglow portion, the glow plugs are continued in pulsed operation, until the sensor detects that the ambient engine temperature has risen to a predetermined level, after which the glow plugs are turned off. Sometimes, during the afterglow cycle, the duty cycle of the glow plugs is adjusted, the duty cycle being reduced as the ambient engine temperature rises prior to glow plug cut-off.
FIG. 1 is a partially schematic, partially block diagram illustrating some of the electrical components of a diesel engine and associated peripheral equipment which form the environment for the present invention. The items illustrated in FIG. 1 do not form part of the present invention per se, but rather are known components in connection with which the present invention, described in detail in succeeding sections, operates. The components illustrated in FIG. 1 are all known and within the skill of one ordinarily conversant with the relevant art. FIG. 1, and this description, is provided for the benefit of those not intimately familiar with this art. FIG. 1 is not intended as a detailed schematic description of these known components. Rather, FIG. 1 is intended only for a general understanding of the relationship among these components.
Toward the left-hand portion of FIG. 1 is a column of eight glow plugs, the uppermost of which is indicated by the reference character G. Operation of the glow plugs is governed by a glow plug controller indicated as GPC. An electric starter motor M, with associated switching, is provided for starting the engine. Batteries B are provided for selectively actuating the starter motor M, and for providing DC electrical power for operating other electrical components of the vehicle and for peripheral components of the engine as needed. The vehicle batteries provide 24 volts DC. The vehicle operates, while running, at 28 volts. Preferably, two batteries in series are provided.
A run/start switch RS is provided for actuating the vehicle ignition circuitry and for selectively actuating the starter.
An alternator A, driven by the engine, provides electrical power for charging the batteries B for providing electrical power to the vehicles loads. The alternator A has an "R tap," (connected to the field) indicated by reference character R.
A fuel solenoid F governs flow of fuel to the engine.
A clutch control C electrically engages and disengages an electric motor driven engine cooling fan.
A wait-to-start lamp W provides a visual indication to an operator when the pre-glow cycle is occurring and it would thus be inappropriate to try to start the diesel engine. A brake warning lamp BW indicates to the operator when a parking brake is set. The brake warning lamp BW also indicates when the start solenoid is engaged. A brake pressure switch BP provides an indication to the operator when a pre-determined amount of force is applied to the service brake pedal. A park brake switch PB, indicates by means of the lamp that the vehicle parking brake is set.
The electrical system of the engine operates several types of electrical loads. One such load is a heater motor indicated generally at the reference character H. Lighting loads are connected to a lead generally indicated by the reference character LL. Certain miscellaneous electrical vehicle loads are indicated by the resistor at reference character VL.
The present invention, as will be described in detail, includes improved circuitry and sub-circuits for governing and safe-guarding operation of the known components illustrated in FIG. 1. Interfaces for connecting the known components of FIG. 1 are provided by an engine connector C1 and a body connector C2, both illustrated in FIG. 1. These connectors interface between the inventive circuitry (not shown in FIG. 1) and the engine and vehicle components shown in FIG. 1.
The concept of controlling glow plugs with solid state controller devices including clocking circuits regulating such functions as glow plug preheat and afterglow control, as well as control of the duty cycle of glow plugs, and temperature related control, is well known. For example, Arnold et al., U.S. Pat. No. 4,882,370, shows a solid state microprocessor controlled device for regulating many aspects of glow plug performance. The Arnold circuitry adjusts the duty cycle of glow plugs as a function of temperature, regulates pre-glow function, and detects undesirable short circuits and open circuits for implementing a disable function. U.S. Pat. No. 4,300,491, to Hara et al., achieves a variable time control of the pre-glow period by means of a plurality of transistors and diodes. Van Ostrom, U.S. Pat. No. 4,137,885 describes means for cyclicly interrupting a glow plug energizing circuit when a maximum temperature is reached. Cooper, U.S. Pat. No. 4,312,307 describes circuitry for control of the duty cycle of glow plugs by means of heat-sensitive switches. Each of the above-identified United States patents listed in this paragraph are hereby expressly incorporated by reference.
It is a general object of the present invention to provide improved glow plug controller circuitry, and mounting and housing structure for such a glow plug controller, to enhance the precision and efficacy of control of operation of the glow plugs of a diesel engine, and to enhance the durability, reliability and ease of assembly of the glow plug controller.